In obtaining a desirable liquid cleanser product, a variety of factors must always be considered. While cleansing, of course, is a primary objective, and is a primary reason anionic surfactants are used, the surfactant system should also be mild to the skin. In addition to mildness, however, it is also important for the formulation to foam well as foaming is often seen as a cue to the consumer of effective cleansing. Traditionally, “mild” cleansers such as Aveeno® or Cetaphil®, for example, are not effective foamers.
Amphoacetates are desirable surfactants because they help cleanse and are milder than anionic surfactants (they are, for example, amphoteric), but they typically don't foam as well as the anionics.
In selecting a mild, good foaming system, applicants have used a combination of amphoacetates and alkanoyl glycinate surfactant because, applicants have found, this combination foams better in foam lather tests than if the same amount of amphoacetates are used with commonly used alkyl sulfates (e.g., sodium lauryl ether sulfate).
Generally, to further enhance mildness of a composition, one might use an emollient(s) (e.g., water soluble humectant emollients, such as glycerin, and/or occlusive moisturizers, such as petrolatum, which block loss of water). The problem is that use of such emollients, especially in low surfactant systems, tends to destabilize phase stability (as measured, for example, by significant viscosity drops when comparing viscosity after 10 days, and having been subjected to freeze-thaw or continuous heat testing).
Quite unexpectedly, applicants have found that increasing levels of emollient to above about 10%, preferably above about 15%, not only increases the mildness of a low surfactant (e.g., less than 10%; preferably less than or equal to 8%, more preferably less than or equal to 7%) alkanoyl glycinate/amphoacetate system, but that it actually significantly enhances phase stability.
As such, applicant are able to obtain a mild composition (e.g., with mild surfactant system), but one that foams adequately, comprises high level of emollient (to further enhance mildness) and still retains stability.